public with sharing class AnimalLocator {
    public static String getAnimalNameById(Integer animalNameId) {
        String animalName = '';
        //New Http 'GET' Request
        Http http = new Http();
        HttpRequest request = new HttpRequest();
        request.setEndpoint('https://th-apex-http-callout.herokuapp.com/animals/:id');
        request.setHeader('Content-Type', 'application/json;charset=UTF-8');
        request.setMethod('GET');
        //Get response
        HttpResponse response = Http.send(request);
        //Parse JSON from the response body
        JSONParser parser = JSON.createParser(response.getBody());
        while (parser.nextToken() != null) {
            // Read entire JSON object
            if (parser.getCurrentToken() == JSONToken.START_OBJECT) {
                AnimalLocator.AnimalList animalList = (AnimalLocator.AnimalList) parser.readValueAs(AnimalLocator.AnimalList.class);
                System.debug(animalList.animal.size());
                //Sort through the list of animals to find one with the matching ID
                //Set the animal name
                for (Integer i = 0; i < animalList.animal.size() ; i++) {
                    if (animalList.animal[i].id == animalNameId){
                        animalName = animalList.animal[i].name;
                        break;
                    } else{
                        animalName = 'Could not find an Animal with a matching ID';
                    }
                }

            }
        }
        return animalName;
    }

    public class AnimalList {
        public List<animal> animal; //This has to be the same name thats in the JSON file.
    }

    //animal Object Wrapper
    public class animal {
        public Integer id;
        public String name;
        public String eats;
        public String says;
    }

}

@isTest
global class AnimalLocatorMock implements HttpCalloutMock{
    global HttpResponse respond(HttpRequest request){
        //Create Fake Response
        HttpResponse response = new HttpResponse();
        response.setHeader('Content-Type', 'application/json;charset=UTF-8');
        response.setStatusCode(200);
        response.setBody(' {"animal":[{"id":1,"name":"Chicken","eats":"Grain","says":"Cluck"},{"id":2,"name":"Dog","eats":"Chicken","says":"Woof"}]} ');
        return response;
    }
}

@isTest
public with sharing class AnimalLocatorTest {
    @isTest
     static void testGetCallout() {
        Test.setMock(HttpCalloutMock.class, new AnimalLocatorMock());
        String result = AnimalLocator.getAnimalNameById(1);
        String expectedResult = 'Chicken';
        System.assertEquals(result,expectedResult);
        result = AnimalLocator.getAnimalNameById(4);
        expectedResult = 'Could not find an Animal with a matching ID';
        System.assertEquals(result,expectedResult);
    }
}